This invention relates generally to methods of forming a ring gear. More specifically, this invention relates to methods of forming a ring gear having internal teeth without the use of machining operations.
Gears are widely used in the mechanical arts to transfer motive force between mechanical components. The gear typically includes gear teeth that engage teeth formed on a cooperable gear or mechanical device to transfer motive force between the two elements. Because the mechanical forces are substantial upon each of the gear teeth, a precise dimensional configuration or profile is required to provide a uniform engagement. This is particularly necessary for gears used in automotive transmissions. To achieve precise dimensional configuration, milling, broaching, and machining operations are generally performed on a gear blank to achieve necessary gear teeth profiles. Generally, teeth formations may be formed in the gear blank and then a subsequent machining operation is performed to provide precise dimensional characteristics necessary to withstand the high loads required of complex motive operations used, for example, in automotive transmissions.
Attempts have been made to cold work or flow form gear teeth profiles in simple gears starting from a blank without the use of additional machining operations. While flow forming and cold working have shown promise in eliminating the necessary machining operations, forming defects are prevalent, have heretofore reduced the ability to use gears having teeth formed only by cold working or flow forming in transmission operations. For example, a gear having angular or slightly helical teeth not parallel to a ring axis that have been formed by cold working or flow forming is known to have inconsistencies resulting from not fully filling mandrel formation elements used to form the gear teeth. Inconsistent forming of the gear teeth in a cold working or flow forming process results in mechanical failures in devices in which the gears are used. Thus, it has been necessary to machine gear teeth used in high speed high torque operations.
Therefore, it would be desirable to provide a method of forming defect-free gear teeth on a gear blank that does not require a secondary machining operation, yet enables the resultant gear to be used in a high speed high torque mechanical device.